Choke control for carburetor



April26, 1966 'r. M. BALL 3,248,096

CHOKE CONTROL FOR CARBURETOR bri inal Filed Dec. 21. 19s;

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United States Patent CHOKE CQNTROL FOR CARBURETO Thomas M. Ball,Bloomfieid Hills, Mich, assignor to Chrysler Corporation, Highland Park,MiclL, a corporation of Delaware Original application Dec. 21, 1961,Set. No. 161,189. Divided and this application Oct. 8, 1963, Ser. No.

4 Claims. (Cl. 261-39) This application is a division of my copendingapplication, Serial No. 161,189, filed December 21, 1961.

This invention relates to improvements in the automatic control of acarburetor for an internal combustion engine and has for an importantobject the provision of improved control means for the conventionalunbalanced choke blade effective to prevent stalling of the engineimmediately after it has been started.

Occasionally when an automatic engine is initially started, a rush ofinlet air blows the choke blade open sufiiciently to cause the engine tostall, particularly during unfavorable weather conditions. It isaccordingly another object of the invention to provide improved simpleand economical means which is highly effective to enable limitedopeningof the choke during starting only, so as to prevent stalling, and whichallows normal choke operation after the engine has been started and thethrottle has once been opened beyond the idle operating condition.

Other objects of this invention will appear in the following descriptionand appended claims, reference being had to the accompanying drawingsforming a part of this specification wherein like reference charactersdesignate corresponding parts in the several views.

FIGURE 1 is a fragmentary and generally schematic view of a carburetorembodying the present invention, portions being broken away toillustrate details of construction, the choke blade being shown in thestarting position.

FIGURE 2 is a view similar to FIGURE 1, showing the choke blade in anidle operating position.

It is to be understood that the invention is not limited in itsapplication to the details of construction and arrangement of partsillustrated in the accompanying drawings, since the invention is capableof other embodiments and of being practiced or carried out in variousways. Also it is to be understood that the phraseology or terminologyemployed herein is for the purpose of description and not of limitation.

Referring to the drawings, an embodiment of the present invention isillustrated by way of example comprising a carburetor for anautomobile'engine, the carburetor including a body having the customaryair inlet induction conduit 11. An unbalancedchoke blade or valve 12 issecured to a rotatable shaft 13 journalled at opposite ends in the body10. The blade 12 is pivotal with shaft 13 and is located-in the upperportion of conduit 11 in accordance with conventional practice. "Athrottle valve 14 secured to a rotatable shaft 15 journalled at oppositeends in the body 10 is provided at a downstream location of the conduit11. A

Suitably located within a portion of the engine so as to be responsiveto an operating temperature thereof is a spiral bi-metallic thermostatspring 16 having a fixed end secured to a fixed spindle 18. A swingingarm 19 pivotal on spindle 18 has an outer swinging end pivotallyconnected to the lower end of an operating link 21. A free end 22 ofthermostat 16 is engaged with arm 19 to urge arm 19 counterclockwisewith progressively increas- The upper end of link 21 is pivotallyconnected at 23 to the swinging end of a crank arm 24 keyed to the chokeshaft 13.

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Keyed to the throttle shaft 15 is a throttle control lever 25 having oneswinging end pivotally connected at 26 with a personally actuatedthrottle link 27. The other end of lever 25 is provided with a threadedboss 28 having an adjustable idle control screw or cam follower29screwed therein. The inner end of screw 29 is adapted to engage astepped cam surface of -a fast idle cam 31 when the latter is in apredetermined cold idle operating position as described below. The cam31 is keyed to a rotatable axial stub 32 journalled on the body 10 andis provided with ,a counterweight portion 33 effective to urge clockwiserotation of cam 31 by gravity force toward a warm operating position.

Throttle lever 25 is normally urged clockwise toward the closed or idleposition illustrated in FIGURES 1 and 2 by a customary throttle returnspring 27a schematically illustrated under tension between a projection25a of lever 25 and a fixed portion 27b of the engine. Foot pedalactuation of shaft 27 is effective to swing lever 25 counterclockwise toopen the throttle 14.

Upon closing movement of choke valve 12, the fast idle cam 31 is swungcounterclockwise to the cold position by means of a link 34 having anupper end pivotally connected at 35 to a crank arm 36 keyed to shaft 13.The lower end of link 34 terminates in an extension 37 which projects ina direction parallel to the pivot axis of cam 31 through a lost motionslot 38 to complete a lost motion pivotal connection between link 34 andcam 31. Slot 38 is formed arcuately within the counterweight portion 33concentrically with the pivot axis of cam 31 to enable opening movementof choke valve 12 independently of movement of cam 31, as describedbelow, by virtue of extension 37 riding within groove 38.

In order to render the position of choke valve 12 responsive to thepressure in conduit 11 downstream of throttle valve 14, a vacuumcylinder 40 formed integrally with body 10 contains a reciprocablepiston 41 therein. A link 54 is provided with an upper end pivotallyconnected at 55 to the outer end of a projection 45 secured to valve12-so as to swing the latter in a clockwise opening movement uponrightward movement of link 54. The opposite end of link 54 is pivotallyconnected at 56 to one end of a short connecting link 57, the other endof the latter link being pivotally connected at 58 to piston 41 tocomplete a toggle connection. A notch 59 is provided in the innersidewall of cylinder 40 adjacent the latters left end to receive adepending projection 60 of link 54, FIGURE 1. The notch 59 isdimensioned so that immediately after starting the engine with thethrottle 14 open, opening of choke valve 12 will be limited byengagement between projection 60 and the right edge of notch 59 toprevent stalling of the engine as described above. right end of cylinder40 is connected by means of duct 46 with induction conduit 11 at alocation downstream of throttle valve 1,4,FIGURE 2, thereby to urgeopening of choke 12 against the force of thermostat spring 16 when thepressure downstream of throttle valve 14 is low, i.e during engineidling.

In the operation of the structure illustrated, throttle 14 is preferablyopen during starting. When the cold engine is initially started andwhile the throttle 14 is still open, limited opening of choke 12, as forexample approximately 10 to a starting position, is enabled by the lostmotion of projection 60 in notch 59. When the throttle 14 issubsequently returned to the idle position in FIG- URE 1, the lowpressure induced downstream of throttle 14 and conducted to the rightside of piston 41 will exert sufficient force on the latter piston topull projection'60 upwardly from notch 59 and enable operation of chokevalve 12 in the customary manner. When the engine is -operated underload, the downward flow of air through The to maintain choke 12 opensufiiciently to prevent extension 60 from re-entering'notch 59,regardless of the temperature condition of thermostat 16. By this time,the danger of engine stalling will have passed, because the stallingtendency described occurs only in' the first two or three seconds ofengine operation.

When screw 29 is in contact with the stepped cam surface, the frictionalcontact between screw 29 and cam 31 resulting from the tension of spring27a is suflicient to prevent pivotal movement of cam 31 in consequenceof the normal forces acting thereon, such as the forces resulting fromcounterweight 33, thermostat coil 16, piston 41, or the downwardlyflowing air in conduit'll acting on the unbalanced blade 12. Inconsequence, when the carburetor parts are in the cold positionillustrated in FIGURE 1 and the engine is idling, the throttle 14 willbe maintained in a fast idle position by reason of screw 29 engaging thefast idlestep of the cam surface of cam 31. At the fast idle position,throttle 14 is cracked slightly open as illustrated in FIGURE 1, so thatthe engine will idle .etfectively in the cold condition. Thereafter,when throttle valve 14 is opened from the fast idle position toaccelerate the engine, the frictional engagement between screw 29 andcam 31 will be released to enable opening of choke valve 12 to the usualoperating condition.

If the throttle 14 is then returned to a cold idle position so as toengage one of the lesser steps of the cam surface of cam 31, the latterwill be locked against swinging movement as aforesaid by virtue of itsfrictional contactwith screw 29. However, the cam 31 will receiveextension 37 within slot 38. Thus if the engine is allowed to run atidle for sufiicient time to relax the closing force of thermostat spring16 as a result of warming of the engine, throttle valve 12 will be freeto open by virtue of movement of extension 37 along slot 38, FIGURE 2.

If the engine is operated in the warm condition under load and is thenturned olf and allowed to cool, choke valve 12 will be locked againstreturn movement to the closed position by contact between fast idle cam31 and screw 29. Accordingly, in order to return the carburetormechanism to the position illustrated in FIGURE 1, throttle 14 mustfirst be opened to release the engagement between cam 31 and screw 29thereby to enable thermostat spring 16 to return choke valve 12 and cam31 to the position of FIGURE 1. Thereafter upon closing of throttle 14,screw 29 will engage the cold starting step of cam 31 as illustrated inFIGURE -1.

I claim:

1. In a fuel charging device for an internal combustion engine, airinlet conduit means, a choke valve in said conduit means having anunbalanced pivotal blade adapted to be urged to an open position by theair flow in said conduit means impinging on said blade, thermostaticmeans responsive to decreasing temperature for yielding- 1y closing saidchoke valve, a throttle valve in said conduit means movable between openand idle position, means to enable limited air flow induced opening ofsaid choke blade to a starting position and to block further openingthereof to prevent a sudden flow of inlet air in said conduit meanssuflicient to stall said engine immediately after the latter has begunto operate under its own power with said throttle valve at its openposition comprising pressure actuated means responsive to the pressurein said conduit means downstream of said throttle valve and operativelycoupled with said choke valve to open the latter in opposition to saidthermostatic means when said throttle valve is at said idle position andto release said choke valve for closing when said throttle valve is atits openposition, operable movement limiting means cooperable with saidpressure actuated means and choke valve to block air flow inducedopening of the latter beyond said starting position when said throttlevalve is at its open position and to release said choke valve foropening when said throttle valve is .at said idle position.

2. In a fuel charging device for an internal combusr tion engine, airinlet conduit means, a choke valve in said conduit means having anunbalanced blade adapted to be urged to an open position by the air'flowin said inlet conduit means impinging on said blade, a throttle valve insaid conduit means movable between idle and open I positions, means toenable limited air flow induced OP'fiIl'. ing of said blade to astartingposition and to block further opening thereof to prevent a sudden flowof inlet air in said conduit means sufficient to stall said engine .im-.mediately after the latter has begun to operate under its own power withsaid throttle valve at an open position comprising a fixed stop, togglemeans including a pair of links having inner ends pivotally connectedand having outer ends relatively movable toward and from each other tofold and unfold said toggle means respectively, said starting positionand being movable out of engagement with said stop to free said chokevalve for opening upon unfolding of said toggle means, pistonmeansconnected with said other end and responsive to the pressure insaid conduit means downstream of said throttle valve when the latter isin an [idle operating condition to move said other end in said directionaway from said one end, thereby to unfold said toggle means and opensaid choke valve.

3. In a fuel charging device for an internal combustion engine, airinlet conduit means, a choke valve in said conduit means having anunbalanced blade adapted.

to be urged to an open position by the air flow in said inlet conduitmeans impinging .on said blade, thermostatic means responsive todecreasing temperaturetfor yieldingly closing said valve, a throttlevalve in said ,conduit means movable between idle and open positions, afixed abutment, means to enable limited opening of said blade to astarting position and to block further opening thereof to prevent asudden flow of inlet air in said conduit means sufficient to stall saidengine immediately after the latter has begun to operate under its ownpower with said throttle valve at an open position comprising anoperating member connected with said choke valve for actuationconjointly therewith and having a movement limiting portion engageablewith said fixed abutment'upon said limited opening of said choke valveblade to said starting position, piston means operably connected with Isaid operating member and responsive to the pressure in said conduitmeans downstream of said throttle valve when the latter is in an idleoperating condition to move said movement limiting portion out ofengagement with said abutment and urge said choke valve blade toward ansition, means operatively connecting said valve and cam.

means to pivot the latter to said cold position upon closing of saidvalve, a throttle valve in said conduit means movable between idle andopen positions, idle control means movable with said throttle valve andengageable with said cam means at the cold position to limit closingmovement of said throttle valve to a fast idle position, 'said idlecontrol means engaging said cam means to prevent pivoting of said cammeans until said throttle valve is opened from said fast idle position,means to enable limited air flow induced opening of said blade to astarting position and to block further opening thereof to prevent asudden flow of inlet air in said conduit means sufiicient to stall saidengine immediately after the latter has begun to operate under its ownpower with said throttlevalve at an open position comprising a fixedstop, toggle means having one of opposite ends connected to said chokevalve to move toward the other of said ends and fold said toggle meansupon air flow induced opening of said choke valve from its closedposition and adapted to unfold and pull said one end to open said chokevalve upon movement of said other end in the direction awayfrom one end,movement limiting means movable with said toggle means into engagementwith said stop on folding of said toggle means to limit said folding andsaid air flow induced opening of said choke valve blade to saidstar-ting position and being movable out of engagement with said stop tofree said choke valve for opening upon unfolding of said toggle means,piston means connected with said other end and responsive to thepressure in said conduit means downstream of said throttle valve whenthe latter is in an idle operating condition to move said other end insaid direction away from said one end, thereby to unfold said togglemeans and open said choke valve.

References Cited by the Examiner UNITED STATES PATENTS 2,408,104 9/ 1946Stanton.

2,420,917 5/ 1947 Sutton et a1.

2,540,607 2/1951 Boyce 261-52 X 2,746,439 5/ 1956 Hunt.

2,762,354 9/ 1956 'Winkler.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, Assistant Examiner.

3. IN A FUEL CHARGING DEVICE FOR AN INTERNAL COMBUSTION ENGINE, AIRINLET CONDUIT MEANS, A CHOKE VALVE IN SAID CONDUIT MEANS HAVING ANUNBALANCED BLADE ADAPTED TO BE URGED TO AN OPEN POSITION BY THE AIR FLOWIN SAID INLET CONDUIT MEANS IMPINGING ON SAID BLADE, THERMOSTATIC MEANSRESPONSIVE TO DECREASING TEMPERATURE FOR YIELDINGLY CLOSING SAID VALVE,A THROTTLE VALVE IN SAID CONDUIT MEANS MOVABLE BETWEEN IDLE AND OPENPOSITIONS, A FIXED ABUTMENT, MEANS TO ENABLE LIMITED OPENING OF SAIDBLADE TO A STARTING POSITION AND TO BLOCK FURTHER OPENING THEREOF TOPREVENT A SUDDEN FLOW OF INLET AIR IN SAID CONDUIT MEANS SUFFICIENT TOSTALL SAID ENGINE IMMEDIATELY AFTER THE LATTER HAS BEGUN TO OPERATEUNDER ITS OWN POWER WITH SAID THROTTLE VALVE AT AN OPEN POSITIONCOMPRISING AN OPERATING MEMBER CONNECTED WITH SAID CHOKE VALVE FORACTUATION CONJOINTLY THEREWITH AND HAVING A MOVEMENT LIMITING PORTIONENGAGEABLE WITH SAID FIXED ABUTMENT UPON SAID LIMITED OPENING OF SAIDCHOKE VALVE BLADE TO SAID STARTING POSITION, PISTON MEANS OPERABLYCONNECTED WITH